The present invention relates to high pressure water washers and more particularly to a chemical injection system for selectively adding a chemical solution to the high velocity water spray discharged by the high pressure water system.
For modern pressure washer systems to be truly effective, it is necessary for such systems to be able to selectively deliver in a rapid and reliable manner a high velocity spray of water both with and without the addition of a chemical cleaning solution. However, for reasons which will become clear, many known pressure washer systems have proven less than completely satisfactory.
In one type of known pressure washer, both water and chemical are injected into the inlet of a high pressure pump assembly with the water and chemical being mixed during the pressurization process. In order to educe a flow of chemical solution into the high pressure pump inlet, it is necessary to create an inlet suction condition in the pump inlet as opposed to an inlet pressure condition. The required pump inlet suction condition might be achieved by an inlet pressure regulator or inlet float assembly. Such a system, referred to hereafter as a pump inlet injection system, also requires check valves and needle and metering valves for controlling the feed rate of water and chemical into the pump. Furthermore, the on-off and metering functions must be done at the pump rather than at the work location itself. Finally, the reaction time required to actually transport the chemical through the high pressure pump and the relatively long output hose or the like is usually at least ten seconds and can even take two minutes or more.
The elaborate and sophisticated components necessary to educe a flow of chemical solution through the high pressure pump makes for a cumbersome and complex washer system which can be exceedingly difficult to maintain and rendered inoperable by failure of one or more of the many working components forming the various valves, as well as the required pressure regulator assembly.
In an attempt to overcome the problems associated with the eductor type of pump inlet injection system, it has been suggested that the chemical solution be mixed with a body of water while in a float tank, with the mixture of water and chemical then being introduced as a single stream into the inlet of the high pressure pump. A main drawback of such a system resides in the inability to selectively control or stop the addition of chemical to the high pressure water stream of the washer system. In other words, there is no effective way to turn off the supply of chemical and provide only an impact spray of pressurized water. This inability to selectively control the flow of chemical eliminates the desirable option of a high pressure water rinse and can result in wasting excessive amounts of the chemical cleaner. In addition, because the chemical always flows through the pump assembly, water control valve and water nozzle orifice, the chemical solution can cause buildups of chemical deposits in these assemblies during regular use and flow stoppage. Where corrosive chemicals are used, this flow path may also result in corrosion and failure of these components. As a result of high maintenence costs, relatively slow response times, and relatively ineffective flow control, pressure washers wherein the chemical solution is injected into an inlet of the high pressure pump have proven less than completely satisfactory.
In a further effort to overcome the problems associated with delivering chemical solution through the water pump inlet, it has been suggested that a second, separate pump assembly be employed for pressurizing the chemical solution to a pressure sufficient to permit its injection downstream of the high pressure pump outlet. This further complicates the overall structure of the chemical injection system, making maintenance of the interrelated pump and valving assemblies time-consuming and costly.
In yet a further effort to overcome the problems associated with providing a chemical solution in the high pressure stream of water, it has been suggested that the high pressure discharge from the pump be routed through a low pressure bypass line in parallel with the usual high pressure line containing the pressure nozzle. This alternate line serves as a chemical application flow path and ends in a separate chemical application nozzle having a large orifice for providing water flow at sufficiently low pressure to permit operation of an eductor for educing chemical into the bypass line. During eductor operation, a significant fraction of the relatively constant pump output is routed through the bypass line, greatly reducing the pressure in both this line and the main line so that the chemical solution is applied to the work surface at relatively low pressure. Low pressure application of the chemical solution is then followed by a high pressure rinse using the usual high pressure flow path and nozzle. The cleaning efficiency of this system is much less than that achievable by impacting a chemical solution at the high velocity available from routing the full pump output through the high pressure water nozzle.
A further drawback of such a washer system is that a relatively large reaction time is still required to reroute the flow and reduce the pressure in the stream to a sufficiently low level so as to allow the eductor assembly to function. Furthermore, the eductor is near the pump and if the length of the line between the eductor and outlet nozzle is increased, as by adding additional hose to the washer system while in the field, the back pressure necessary to overcome the additional pressure drop often makes it impossible to reduce the pressure sufficiently so as to actuate the chemical eductor assembly. Also, any kinks in the hose, chemical deposits in the nozzle or other flow restrictions that may occur during use of the washer system can increase the back pressure to a level where it is difficult, if not impossible, to actuate the chemical eductor assembly in the bypass line.
In conjunction with the aforementioned approaches of chemical delivery systems, the use of electrically controlled solenoid valves, actuation switches at the operators handle, transformers and other electrical and electronic components sometimes appear to improve speed, economy and convenience of chemical delivery.
However, besides being unusually expensive in various degrees of sophistication, inherently such installations become inoperable after short initial operation periods. The maintenance trouble shooting on such over sophisticated systems is usually beyond the capability of ordinary maintenance personnel and these machines therefore become unusable.
As will become clear hereafter, the present invention provides an immediate action chemical addition system which overcomes the problems confronting known pressure washer assemblies as discussed hereabove, such as avoiding excessively complex mechanisms having relatively long reaction times and other drawbacks.